I had to bend up a piece of sheet metal when I did my CJ. I bent up a piece that fit like I needed it to and then pop riveted it in. The flares cover the rivets on the outside of the fender and you can paint or undercoat the rivets in the fender well.
'86 CJ7, 258 w/Mopar MPI, 4.56 gears, rear Detroit/front Truetrac, full cage, OBA, 8274, 4" lift via Alcans/Rancho, 35's on beadlocks, other stuff. Built for rocks, mud is a four letter word.